1. Field of the Invention
This invention relates generally to semiconductor devices, and more particularly, to the testing thereof.
2. Discussion of the Related Art
FIG. 1 shows a plan view of a typical pin grid array semiconductor device 10. The device 10 includes a substrate 12 on which is mounted a semiconductor processor 14. Also mounted on the substrate 12 are a plurality of fuses L1, L2, L3, L4 etc. (each of which may be blown by a laser) in operative association with various resistor packs R1, R2, R3 etc. These fuses are used to configure the processor in various ways, for example the frequency of the processor, the voltage thereof, etc. As an example, the fuses L2, L3, L4 are used to configure the frequency of the processor 14. Each of the fuses L1 (one shown in FIG. 2) is connected to a pin 16 of the device 10, and is also connected to a BP pair 18, i.e., (1) a fuse L3A connected in series with a resistor 20, and (2) a fuse L3B connected in series with a resistor 22, the fuse L3A and resistor 20 being in parallel with the fuse L3B and resistor 22. Initially, either the fuse L3B is blown by a laser (FIG. 3), or the fuse L3A is blown by a laser (FIG. 4), the blowing of only fuse L3B resulting in a pull up on the BP pair 18, Mile the blowing of only fuse L3A results in a pulldown on the BP pair 18. Then, each fuse L1 is blown by a laser to disconnect its associated BP pair 18 from the pin 16 (FIG. 5). This ensures that the frequency of the processor 14 cannot be reconfigured thereafter.
Next, a laser level test is undertaken for verification that laser cutting of the fuses L3 has been done correctly. However, because the fuse L1 has been blown, the fuses of each BP pair 18 are no longer connected to a pin of the pin grid array device. Thus, a number of fuses cannot be accessed to verify their state.
What is needed is apparatus which allows fill testing of a device after a laser cutting process has been used to configure the device and pins of the device have been disconnected from internal circuitry thereof.
The present apparatus for testing an electrical device which includes fuses has a resilient, compressive, insulating base mounted to the underside of a thermal head. A plurality of conductive elements are mounted on the base, in parallel, adjacent but spaced apart relation. With the thermal head in close proximity to the electrical device, a number of the conductive elements are caused to be brought into contact with and bridge a fuse, so that connection is provided between one side of the fuse and the other.
The present invention is better understood upon consideration of the detailed description below, in conjunction with the accompanying drawings. As will become readily apparent to those skilled in the art from the following description, there is shown and described an embodiment of thus invention simply by way of the illustration of the best mode to carry out the invention. As will be realized, the invention is capable of other embodiments and its several detail are capable of modifications and various obvious aspects, all without departing from the scope of the invention. Accordingly, the drawing and detailed description will be regarded as illustrative in nature and not as restrictive.